Crosstac Buttstock / Sling Upgrade Kit Black Regular. For those who didn't the original buttstock this kit includes all the hardware you need to replace the original. We HIGHLY recommend replacing the buffer tube buffer and bolt with new Crosstac Original buttstock parts as Crosstac original buttstock pins and sling swivels are not the best long-term solution for connector failure - use the Crosstac Original buttstock replacement pins - these are the same type of connectors that are used on our B2 adapter. It is highly recommended that you back order a B2 conversion kit as the direct impact on weapon handling and accuracy will be minimal - if any - on the new buttstock. This kit also includes a replacement swivel for those who already have a sling or want to make a conversion for a sling swivel. Specifications for Crosstac Buttstock / Sling Upgrade Kit: Manufacturer: Crosstac Length: Regular Included Accessories: HK style Connectors Package Contents: Crosstac Buttstock / Sling Upgrade Kit Crosstac 135026-BLK: Buttstock / Sling Upgrade Kit Black Regular